The present invention relates to a solar pump system and a method of controlling the solar pump system.
A solar pump system refers to a system for driving a pump through an inverter using energy generated by a solar module and generating and supplying fresh water. Such a solar pump system can most efficiently supply water and electricity. The solar pump system is used for supply of drinking water or agricultural water or seawater desalination in an area in which water supply infrastructure is insufficient. In addition, the solar pump system is considered as an optimal system for pumping and supplying underground water without supplying additional energy in a remote area, in which it is difficult to supply power, to solve water and electric power shortage in the remote area. The Indian government permitted installation of 50,000 solar pumps in 2004, for irrigation and drinking water supply, and has increased the number of solar pumps up to now.
Meanwhile, one important control method in a solar inverter for generating power using sunlight is a maximum power point tracking (MPPT) control method. The solar inverter always generates maximum power through MPPT control for tracking a maximum power generation point of a solar cell.
A basic control method of MPPT control methods is a hill climbing method. In this method, a duty ratio is changed by a predetermined displacement to find a maximum power point. In the hill climbing method, a controller is simple but a maximum power point estimation speed is low when an amount of solar radiation is rapidly changed.
A most general control method of the MPPT control methods is a perturbation and observation method. In this method, power change is measured according to increase or decrease of a voltage to perform operation at a maximum power point. However, in this method, when the amount of light is low, control properties may deteriorate.
Meanwhile, in an incremental conductance method of the MPPT control methods, a property that a solar cell outputs a maximum value when impedance of a load is equal to that of the solar cell is used. The incremental conductance method is excellent in terms of tracking performance but requires many complex operations.
FIG. 1 is a diagram showing the configuration of a conventional solar pump system.
In the conventional solar pump system, a controller 200 for controlling an inverter 100 receives input and output currents of the inverter 100 and the inverter 100 detects a voltage and current using a sensor to perform MPPT control. The conventional solar pump system should accurately detect the voltage and current. However, as detection accuracy increases, the price of the sensor provided in the solar pump system increases.